1. Field of the Invention
The present invention is related to wide band linear amplifiers and more particularly to resistively loaded wide-band high frequency linear amplifiers.
2. Background Description
Wide band multi-channel communication systems require wide band amplifiers with a high degree of linearity to avoid second and third order affects arising from the large number of potential carrier interactions. So, second and third order effects must be minimized for maximum linearity in the amplifier. Typically, some form of automatic gain control is included which reduces gain to compensate for large input signals, trading uniform gain for extended signal linearity.
Unfortunately, since for a typical integrated circuit amplifier output current flow is unidirectional, i.e., from a supply to supply return or ground, these prior art amplifiers typically steer current to/away from resistive loads, significantly changing the DC operating point of the amplifier. These operating point shifts can result in poor amplifier linearity and limit the amplifier gain range. If too large of a current is steered toward the resistive load, the output voltage can decrease significantly and can cause the amplifier to saturate, resulting in poor linearity, as well as degraded amplifier signal response and bandwidth. If too small of a current is steered toward the output resistive load, the output voltage can increase significantly, resulting in catastrophic device failure.
Thus, there is a need for a stable load bias for wide band multichannel amplifiers to maintain the amplifier at an intended operating bias point.